This invention is generally directed to fluid flow control valves and methods of regulating fluid flow therethrough and, more particularly, to valves which are responsive to the temperature of fluid flowing therethrough for purposes of reducing flow when temperatures above a predetermined temperature are sensed. The method of the invention and the valves use fluid pressure to ensure effective valve responsiveness dependent upon fluid temperature. The invention is also directed to such valves and methods of manually adjusting the valves to vary flow rate when fluid temperatures are below the predetermined temperature.
It is often necessary to control the flow of hot gases or liquids to ensure industrial processing or to protect individuals from injury due to exposure. By way of example, in commercial and residential hot water systems intended for personal use, water temperatures will frequently exceed 125.degree. to 130.degree. F. At these temperatures, an individual can easily be scalded or burned by contact with the hot water in a few seconds. The regulation of water temperature becomes more critical in commercial environments where a large source of supply is necessary during relatively short demand periods, such as mornings and evenings, when water temperatures are elevated in boilers or heaters to ensure hot water is available to individual outlets. Even in household environments, a hot water heater may be set to a temperature in excess of 130.degree. F. for purposes of providing sufficiently hot water for bathing, dishwashing and clothes washing. Under these circumstances, it is critical to ensure that individuals are protected from the hot water to prevent injury.
One of the problems with regulating fluid supplies depending upon temperature is the cost of control systems which can adequately function. The use of electronically controlled valves has not been satisfactory for commercial and residential uses. However, through the development of temperature sensitive metal alloys, mechanically operated valves have been made which are mechanically actuated in response to fluid temperatures at lower costs.
Such mechanical valves incorporate springs made of metal alloys which vary their force depending upon the temperature of a fluid to which they are exposed. Such memory alloy springs exhibit a first biasing force in a martensitic state and a greater force at elevated temperatures in a austenitic state. These type of springs can be treated so as to exhibit a transformation from the martensitic to the austenitic state at predetermined temperatures so that they change their biasing force dependent upon a selected or predetermined temperature. Examples of valves incorporating shaped memory alloy springs are disclosed in U.S. Pat. Nos. 4,778,104 to Fisher, 4,848,388 to Waldbusser, 5,259,554 to Ewing, et al. and 5,261,597 to Perlman, et al.
Many prior art valves incorporating shaped memory alloy springs are not designed to operate consistently within a preselected temperature range, especially if fluid pressures within a supply line vary. In most systems, springs are placed in line with the fluid flow through a valve and are subject to variations in fluid pressure. Other valves which incorporate shaped memory alloy springs to provide for automatic control of a valve mechanism dependent upon the temperature of the fluid flowing therethrough do not allow springs to be continuously in heat exchange relationship with fluid flowing through the valves and therefore are not adequate for many uses.
In U.S. Pat. No. 5,123,593 to Rundle, a fluid flow controller for regulating a source of hot liquid is disclosed which includes a pair of springs which operate to open and close a ball valve with respect to a seat within the controller. A first shaped memory alloy spring is placed in communication with fluid flowing from a supply source and is activated by the temperature of the fluid through the controller upstream of the valve seat. When the fluid temperature increases above a predetermined temperature, the first spring activates the ball valve to close against the valve seat and thereby terminate fluid flow. The second spring is mounted on the downstream side of the ball valve and is operable when the fluid temperature to the inlet of the flow controller drops below a predetermined temperature to overcome the pressure of the first spring and thereby open the ball valve to allow fluid flow through the controller. This type of valve does not provide for any manual adjustment of the flow rate through the valve. Further, when the first spring is activated, flow of fluid through the valve is terminated and there is no provision for allowing fluid from the source to trickle through the closed valve so as to be in heat exchange relationship with the first spring. Therefore, the first spring cannot react quickly to upstream changes in fluid temperature to permit the valve to be re-opened in a timely manner.